1. Field of the Invention
The invention relates to Automatic Network Discovery and Selection Function (ANDSF) mechanisms (and the like) and to the use of ANDSF data or other network selection data.
2. Description of Related Art
Many mobile communication devices are able to make use of more than one communication access technology. For example, some mobile communication devices are able to make use of both the 3GPP standard and WLAN (wireless local area network).
Providing a mobile communication device with alternative communication technologies has a number of potential advantages. For example, the mobile communication device may be able to function in areas where only one of a number of access technologies is available. Also, if a user requires a low cost connection, then the cheapest of a number of available connection options can be chosen. Alternatively, if a user wants to send a large amount of data over a connection, then a connection with a high available bandwidth can be chosen.
It is known to provide mobile communication devices with information regarding access technologies that are available. Access Network Discovery and Selection Function (ANDSF) mechanisms allow a mobile operator to provide subscriber devices with inter-system mobility policies for automatic, intelligent network selection in a heterogeneous network environment, where a plurality of different non-3GPP access technologies are available together with 3GPP or fulfilling gaps where 3GPP is not available.
FIG. 1 is a block diagram of a system, indicated generally by the reference numeral 1, comprising a mobile communication device 2, an ANDSF server 4, a first mobile network 6 and a second mobile network 8.
In the use of the system 1, the ANDSF server 4 provides information to the mobile communication device 2 regarding the priority in which the access networks available to the mobile device (such as the networks 6 and 8) should be accessed. The mobile communication device requests this priority information from the ANDSF server 4, and the ANDSF server returns the requested data to the mobile communication device. The mobile communication device 2 may choose the network to be used with ANDSF communication according to existing network selection information or by any other means available to the mobile device.
FIG. 2 is a flow chart showing an algorithm, indicated generally by the reference numeral 10, showing an exemplary use of the system 1 by the mobile communication device 2.
The algorithm 10 starts at step 12, where ANDSF information is obtained. The ANDSF information may, for example, be provided (by the ANDSF server 4) on request from the mobile communication device 2 (in a “pull” mode) or may be provided in a manner determined and initiated by the ANDSF server (in a “push” mode).
The ANDSF server 4 provides a number of policies for connecting the mobile communication device 2 to networks (such as the first mobile network 6 or the second mobile network 8). Priorities are assigned to the various policies and, at step 14 of the algorithm 10, the highest priority valid policy is applied by the mobile communication device 2. A policy is considered to be “valid” if it meets a number of validity conditions. Such conditions may, for example, relate to location or the time of day.
The policy selected at step 14 will have a number of access network options associated with it. The access network options will be prioritized within the policy. At step 16 of the algorithm 10, the highest priority access network option of the selected policy is selected at the mobile communication device 2.
The algorithm 10 moves to step 18 where it is determined whether or not the highest priority access network option of the selected policy has resulted in a successful connection to an available network. If a network connection has been made, then the algorithm 10 terminates at step 24. If a connection has not been made then the algorithm 10 moves to step 20, where it is determined whether or not the selected policy has any more (lower priority) access network options available.
It should be noted that ANDSF information does not define when a network connection is considered to be good enough. Even if a mobile communication device is able to connect to a network, the network quality may still be low. It is left to the mobile communication device to decide whether a given network fulfills its own requirements for the connection. If the network quality is too low, then the mobile communication device can choose the next preferred network in the policy.
If no further access network options exist, the algorithm 10 terminates at step 24. If further access network options do exist, then the next highest priority access network is selected at step 22. The algorithm 10 then returns to step 18, where it is determined whether or not the newly selected access network results in a successful connection to an available network. If a connection is made, then the algorithm 10 terminates at step 24. If a connection is not made, then the algorithm 10 moves to step 20, as discussed above.
The algorithm 10 continues until either a successful connection is made or all access network options of the selected policy have been tried. In some implementations of ANDSF systems, if the highest priority valid policy does not result in a connection being made, then no further efforts are made to make a connection. In other implementations, if the highest priority valid policy does not result in a connection being made, then the next highest priority policy (if any) is used and steps 16 to 24 of the algorithm 10 are repeated using that policy.
In addition to providing network selection policies, ANDSF allows mobile operators to provide access network discovery information (ANDI) to assist user equipment (UE) in detecting access networks specified in the ANDSF policy rules. Policies are used to list preferred access networks in any given location or time.
Discovery information consists of radio technology specific information like frequencies and channels. This is particularly important, for example, for WiMAX where blind scanning of the whole frequency domain can take a considerable period of time (perhaps as much as 15 minutes or more) and can use considerable battery resources.
Both policies and discovery information can have validity area, expressed for example using 3GPP Cell Identifier or tracking area data. Typically, an ANDSF server runs in an operator network and delivers the policies and discovery information to a user device either on request from the user device (pull mode) or at the operator's preference (push mode).
When the ANDSF mechanism was first proposed, it was only intended to provide data that is valid within the area of a single public land mobile network (PLMN). This network (the “home” network) of the user device was the only network for which ANDSF data was provided. More recently, it has been proposed to provide roaming support using ANDSF data. This means that when a particular user device moves from a home network to a visited network, the user device can still make use of ANDSF information. In one arrangement, when roaming, a user device is able to contact a home operator ANDSF (H-ANDSF), a visited operator ANDSF (V-ANDSF) or both.
FIG. 6 is a block diagram of a system, indicated generally by the reference numeral 60, comprising a mobile communication device 62, a visited operator ANDSF (V-ANDSF) 64, a home operator ANDSF (H-ANDSF) 65 and a network 66 (such as a 3GPP IP access network or some other non-3GPP IP access network). As shown in FIG. 6, the mobile communication device 62 and the V-ANDSF server 64 are located within a VPLMN and the H-ANDSF server 65 is located within a HPLMN. The HPLMN and VPLMN are separated in FIG. 6 by a dotted line 68. Accordingly, in the system 60, the mobile communication device 62 is roaming in the network VPLMN and using the network 66 of the VPLMN to do so.